1. Field of the Invention
The present invention relates to a diesel engine to which a continuously variable valve lift actuator (CVVA) is applied. More particularly, the present invention relates to a system for controlling a continuous variable valve lift actuator of a diesel engine and a method thereof that stabilizes exhaust gas and improves performance by variably controlling lift and timing of intake and exhaust valves based on a combustion state and a driving purpose.
2. Description of Related Art
Generally, an internal combustion engine burns an air-fuel mixture in a combustion chamber so as to generate power. A camshaft is driven by a timing belt connected to a crankshaft, and intake and exhaust valves are operated thereby. Air flows into the combustion chamber while the intake valve is open, and gas burned in the combustion chamber is exhausted while the exhaust valve is open.
Lift and timing of such intake and exhaust valves should be preferably controlled according to a rotation speed of an engine so as to achieve optimal engine performance.
To achieve optimal operation of the intake and exhaust valves according to the rotation speed of the engine, a cam operating the intake and exhaust valves has been researched and designed to have a plurality of shapes. Also, a continuously variable valve lift (CVVL) system that controls lift of the intake and exhaust valves to be changed according to the engine speed has been researched.
Such a CVVL system includes a drive shaft opening or closing the intake and exhaust valves, an actuator controlling the lift of the intake and exhaust valves, and a control shaft controlling the actuator together with the drive shaft so as to control the lift of the intake and exhaust valves.
There are many techniques for controlling a throttle valve in a gasoline engine so as to control exhaust gas and combustion and to enhance fuel mileage. On the contrary, there is no technique for stabilizing exhaust gas and improving combustion performance through control of the CVVL system in the diesel engine.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.